Malachai is one of rogue Judicator Alain's three disciples. Formerly a pirate from a gang called the Berserkers, Malachai was offered his life in exchange of his service by Judicator Alain after he and Judicator Halko cracked down on the gang, effectively exterminating it almost to a man. Along with the trio of men taken in as disciples by Judicator Halko, Malachai is one of the few survivors of the original Berserker gang that used to be the menace of Aquila Reach. He now serves as Alain's personal attack dog, doing the dirty work that requires little subtlety and plenty of violence.
As is typical for a Judicator, especially one of questionable background, little is known about Malachai's past other than him being a member of a notorious pirate gang. However, his high tier of rather specialized augmentation, his combat prowess and heraldry elements featured on his armor suit strongly suggest an extensive military background, possibly the Alpha Legion. If true, Malachai's fate isn't really surprising - with lulls of fighting in the perpetual war between the Imperium and its traditional enemies, many military men find themselves out of work, and often have trouble integrating into civilian lives. Many such misfits consequently turn to crime and are welcomed into pirate crews and criminal gangs for their combat expertise, the best oftentimes serving as personal bodyguards and enforcers of prominent crime barons.
Whatever the reason for his joining, Malachai used to be a member of a pirate gang called Berserkers, known among other things for their Viking-themed attires, mannerisms and practices, and for their fierce rivalry with the equally-outlandish Dandy Boys who were known for their Victorian-themed personae and outfits - perhaps chosen to highlight their difference from the uncouth and barbarous Berserkers.
His time with the Berserkers came to an abrupt end when Judicator Alain and Judicator Halko decided to put an end to the gang's reign of terror sometime between the events described in Access Violation and A Blood Debt. Malachai was among the handful of men spared during the wholesale slaughter the two Judicators visited upon the Berserker gang. Having impressed the Judicators with their tenacity, the four known survivors of the extirpation were given an offer they couldn't refuse - their lives in exchange for their allegiance and perpetual service.
Malachai is a vicious and cold-blooded killer with apparent sadistic inclinations, as is evidenced by his savage murder of Nathan Epstein and his threats of infanticide, rape and torture to Riva Geller at the start of Flight of the Polunochnaya. Given his background and his treatment of Nathan, there is little doubt about Malachai being capable of making good on his threats, though it is unclear whether he simply indulges his own bestial urges or is acting deliberately on Alain's explicit orders. Whatever the case, Malachai is certainly not a man to be trifled with.
Despite his savage looks and mannerisms, Malachai is by no means a mindless brute, and is in fact at least as intelligent as his former companion Bjorn - and quite possibly also more independent-minded, as is attested by his apparent refusal to adopt a Viking-themed name in keeping with the traditions of his old gang. While certainly not much of a schemer himself, Malachai is intelligent enough to understand the schemes of others (such as his master Alain) sufficiently well to carry out his part in them effectively and avoid accidentally unraveling them through careless actions or words.
Malachai holds a grudging loyalty towards Alain - mainly because of his first-hand experience with what happens to Alain's enemies. While there is little reason to doubt that Malachai would betray Alain if an opportune moment presented itself, it is unlikely to ever happen - as long as the rogue Judicator is alive, Malachai simply doesn't dare to disobey or turn on him.
His attitudes towards his fellow disciples is somewhat condescending. Malachai holds disdain for Inessa and her hound-like loyalty to Alain, viewing her as a dead weight lacking the innate ruthlesness necessary to survive against the whole galaxy, and hence a threat to his own survival. He also openly despises Ignatius for being a "deranged fop", holding an equal dislike for the latter's twisted scientific experiments and sense of fashion (evidently reminiscent of the Berserkers' former Dandy Boy rivals). That being said, Malachai reluctantly cooperates with the other disciples, recognizing the practical necessity and also simply wishing to avoid Alain's wrath that is bound to strike any who dare to let their petty differences get in the way of the renegade Judicator's schemes.
Malachai is likewise none too fond on his former brothers-in-arms who now serve Judicator Halko, viewing them as incompetent brutes and only holding some respect for Bjorn as the most intelligent and professional of the trio. Malachai seems to despise drama and pomp, a trait that perhaps contributed to his refusal to adopt a Viking-themed name against the conventions of his old gang.
Overall, Malachai is a pragmatical cynic holding no permanent allegiance or loyalty to anyone other than himself and merely pledging himself to a cause when it serves his own self-interest, be it power, glory and wealth or simple survival. A positive quality of his is that he makes no effort to hide it, having frankly told even Alain himself that the desire to avoid the fate of his former associates is the only reason why he agreed to serve the Judicator.